How Were Date And Mint Mark Punches Made?

Bringing this back to the original post, I was wondering if there was anything like an "error punch".

I found the answer. In 1864, they used a defective digit punch on the dies for the Copper Nickel IHCs. The punch leaves what appears to be a repunched 4, but there is no interest or premium for this "variety" because, unsurprisingly, it exists on over half the dies (Snow Vol 2).

As for "who would care", I would imagine this would be a very important piece of knowledge for those looking for RPDs. Misinformation could create a premium when one doesn't exist.